Doxycycline has anti-tumour effects in a range of tumour systems. The aims of this study were to define the role mitochondria play in this process and examine the potential of doxycycline in combination with gemcitabine. We studied the adenocarcinoma cell line A549, its mitochondrial DNA-less derivative A549 ρ° and cultured fibroblasts. Treatment with doxycycline for 5 days resulted in a decrease of mitochondrial-encoded proteins, respiration and membrane potential, and an increase of reactive oxygen species in A549 cells and fibroblasts, but fibroblasts were less affected. Doxycycline slowed proliferation of A549 cells by 35%. Cellular ATP levels did not change. Doxycycline alone had no effect on apoptosis; however, in combination with gemcitabine given during the last 2 days of treatment, doxycycline increased caspase 9 and 3/7 activities, resulting in a further decrease of surviving A549 cells by 59% and of fibroblasts by 24% compared to gemcitabine treatment alone. A549 ρ° cells were not affected by doxycycline. Key effects of doxycycline observed in A549 cells, such as the decrease of mitochondrial-encoded proteins and surviving cells were also seen in the cancer cell lines COLO357 and HT29. Our results suggest that doxycycline suppresses cancer cell proliferation and primes cells for apoptosis by gemcitabine.

1 We have investigated an aspect of the regulation of cortical pyramidal neurone activity. Microdialysis was used to assess whether topical application of drugs (in 10 M1) to fill a burr hole over the frontal cortex, where part of the corticostriatal pathway originates, would change concentrations of the excitatory amino acids glutamate and aspartate in the striatum of the anaesthetized rat. 2 Topical application of N-methyl-D-aspartate (NMDA, 2 and 20 mM) dose-dependently increased glutamate and aspartate concentrations in the striatum. Coapplication of tetrodotoxin (10 ,uM) blocked the NMDA-evoked rise in these amino acids. A calcium-free medium, perfused through the probe also blocked the rise, indicating that it was due to an exocytotic mechanism in the striatum. 3 It was hypothesized that the rise observed was due to an increase in the activity of the corticostriatal pathway. As 5-hydroxytryptaminelA (5-HTIA) receptors are enriched on cell bodies of corticostriatal neurones, a selective 5-HTIA-antagonist (WAY 100135)

1 We studied the effect of bradykinin on plasma exudation in the airways of the anaesthetized guineapig in vivo. Tissue content of extravasated Evans blue dye was used as an index of protein exudation in the larynx, trachea, main bronchi and intrapulmonary airways (i.p.a.). 2 Bradykinin increased the content of Evans blue in all tissues studied in a dose-related manner. The response was greatest in the main bronchi and i.p.a., less in the trachea and least in the larynx. A dose of 47 nmol kg-1 was the lowest tested which caused significant (P < 0.001) plasma exudation with increases in leakage above control values of 256% in the larynx, 405% in the trachea, 394% in the main bronchi and 485% in intrapulmonary airways. 3 Leakage was significantly (P < 0.05) increased above control values by 1 min after bradykinin (47nmol kg-1) in the main bronchi and intrapulmonary airways and was maximal in all airways 5min after bradykinin. Although reduced by 15min, the tissue content of dye was still significantly (P < 0.05) increased 2 h after bradykinin. 4 The prolonged tissue dye retention was due to a later phase of slow and maintained exudation preventing full clearance of dye after the initial response. 5The initial phase of leakage was partially attenuated by the platelet activating factor (PAF) receptor antagonists WEB 2086 or BN 52021, by indomethacin or by inhibiting sensory nerve activation by opioid anaesthesia: it was not affected by mepyramine and cimetidine nor by the sulphidopeptide leukotriene receptor antagonists FPL 55712 or ICI 198,615. Adrenoceptor blockade of the anti-leakage effects of endogenously-released catecholamines significantly (P < 0.05) enhanced leakage. 6 The later phase of plasma leakage was completely inhibited by the PAF antagonists. 7 We conclude that, in guinea-pig airways in vivo, the initial phase of bradykinin-induced plasma exudation is mediated in part by PAF, sensory nerves and prostaglandins, whereas the later, prolonged phase of leakage is mediated exclusively by PAF. If bradykinin is generated in asthma, its potent and prolonged effects on plasma leakage may contribute significantly to airway oedema and may be involved in the development of bronchial hyperresponsiveness.

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Physostigmine, the acetylcholinesterase inhibitor (0.3 mg/kg, i.m.), increased extracellular glutamate but not aspartate concentrations in the striatum of anaesthetised rats, determined using microdialysis and HPLC. The rise was both tetrodotoxin and calcium dependent. In contrast, neither physostigmine (10 µM) added to the perfusion fluid nor vehicle (injected intramuscularly) affected amino acid concentrations. To obtain evidence that the action of acetylcholine was to modulate positively cortical pyramidal neurone activity via the M1 receptor, the selective M1 agonist PD 142505‐0028 (10 µM) was topically applied to the frontal cortex. Like physostigmine, PD 142505‐0028 rapidly increased glutamate but not aspartate concentrations in the striatum. Moreover, the effect of intramuscular physostigmine was blocked by a topically applied M1 antagonist. These new data add to our hypothesis that cholinomimetics increase pyramidal neurone function.